A conventional interrupter unit is described, for example, in French Patent No. 2 491 675 A1. According to the design of the unit described there, a nozzle body made of insulating material is held in a metallic cylindrical component of the interrupter unit.
Under the influence of the hot switching gases, such a nozzle body made of insulating material may become deformed due to the effect of either high temperature or high gas pressure, and it may ultimately become detached from the fastening. The function of the circuit breaker is then no longer guaranteed, since without a properly operating nozzle the arc can no longer be blown out or reliably extinguished.